title: A method for estimating the residual risk of transfusion-transmitted HBV infection associated with occult hepatitis B virus infection in a donor population without universal anti-HBc screening.
abstract: OBJECTIVE
  This report describes a method for estimating the risk of transfusion-transmitted HBV infection attributable to blood components from donors with occult hepatitis B virus infection (OBI) applicable where universal anti-HBc screening is not performed.
  
  
  METHODS
  In the context of parallel HBsAg and individual donation HBV DNA testing, we developed a mathematical function p(OBI) to estimate the probability of failing to detect [p(NAT nondetection)] a potentially infectious [p(transmission)] donation from a donor with OBI.
  
  
  RESULTS
  Among 1 312 451 donations tested for HBsAg and HBV DNA, 29 (from 17 anti-HBc reactive donors classified as OBI) were individual donation NAT negative, giving a p(NAT nondetection) of 2·2096 (95 CI: 1·538-3·173) × 10(-5) . To date, lookback on OBI donors has identified 35 (8·2%) recipients with evidence of current or past HBV infection among 427 tested recipients. After correcting for the background anti-HBc rate in recipients, this results in a p(transmission) of 0·0384 (0·0167-0·0601). The product, pOBI is 1 in 981 920 (95% CI: 437 181-3 223 701). When this is summed with the WP risk for the 2011-2012 period, the overall HBV residual risk estimate is 1 in 538 224 (95% CI: 209 732-1 552 443).
  
  
  CONCLUSIONS
  We estimate the OBI residual risk in Australia is approximately 1 in 982 000 per unit transfused, and this risk represents 55% of the total HBV residual risk and is declining as consequence of ID-NAT identifying repeat donors with OBI.
authors.affiliation: Australian Red Cross Blood Service, Melbourne, Vic., Australia.
authors.forename: C R
authors.initials: CR
authors.lastname: Seed
authors.forename: P
authors.initials: P
authors.lastname: Kiely
mesh_terms: D001315:Australia; D001782:Blood Donors; D004279:DNA, Viral / Q000097:blood; D006403:Hematologic Tests / Q000379:methods; D006509:Hepatitis B / Q000517:prevention & control / Q000635:transmission* / Q000821:virology; D006510:Hepatitis B Antibodies / Q000097:blood; D006514:Hepatitis B Surface Antigens / Q000097:blood; D006515:Hepatitis B virus / Q000235:genetics / Q000276:immunology / Q000302:isolation & purification*; D006801:Humans; D012306:Risk; D065227:Transfusion Reaction
chemical_list: D004279:DNA, Viral; D006510:Hepatitis B Antibodies; D006514:Hepatitis B Surface Antigens
keywords: NAT testing; blood donation testing; residual risk estimation